Gumbo filé is an important ingredient in Creole and Cajun cuisine. Gumbo filé, or filé powder, is the finely ground, dried leaves of the sassafras tree. In addition to its thickening properties, it adds a slightly smoky or a hint of root beer-like flavor to food. While nothing can substitute for the subtle flavor that gumbo filé imparts, a number of ingredients can be used in its place as a thickener.
When thickening gumbo with a substitute for filé powder, remember that filé is added by the diner at the table. For three reasons, filé powder is seldom added to gumbo by the cook: It becomes stringy and unappetizing when heated, not everyone likes its distinctive flavor and aroma, and some people like their gumbo thicker than others do. Keep this last reason in mind when using substitutes, so that you do not over-thicken your gumbo, as most substitutes must be added during the cooking process.
Okra, the seed pod of the Abelmoschus esculentus plant, is a standard ingredient in most gumbo recipes. When cooked, okra exudes a mucilaginous form of fiber that thickens whatever liquid it is mixed with. This viscous substance makes okra acceptable as a thickener in place of gumbo filé. Extra okra for thickening should be added whenever you add the okra that is already in the recipe.
A slurry of cornstarch mixed well with water can be used to thicken your gumbo in place of filé powder. It is flavorless and will not alter the taste of your gumbo. This thickener should be added just before serving, as it thickens very rapidly. One tablespoon of cornstarch mixed with an equal amount of cold water will thicken 1 cup of liquid. Because cornstarch tends to clump quickly, whisk the cornstarch slurry slowly into your gumbo, watching carefully to avoid over-thickening the stew.
Like cornstarch, arrowroot must be mixed into a slurry with an equal amount of water and added to the gumbo prior to serving. Arrowroot has a neutral flavor and stands up better to freezing, making it a better choice than cornstarch if you are planning to freeze some gumbo for later.
Roux is also used for thickening gumbo, so making extra may give you the consistency you want. It is cooked first; vegetables, seafood and other ingredients are added after the roux is prepared. Cook this combination of equal parts of butter and flour until the flour darkens and combines completely with the fat. Depending on your skill level and the type of gumbo, you will want a chocolate, red-brown, or brick colored roux for your gumbo. A well-made roux adds a distinctive nutty flavor to the stew. Keep in mind that the darker the roux is, the less thickening ability it has.